People are bad at reporting what they eat. That's a problem for dietary research

Original Article ↗ Hacker News Discussion ↗

Limits of Dietary Research & Confounding

  • Many commenters argue most nutrition studies are near-impossible to do well: too many confounders (activity, income, culture, health-consciousness, sleep, genetics, microbiome).
  • Strong skepticism that “large N” averages these out, since diet often correlates with lifestyle (e.g., people who eat more vegetables also exercise more and see doctors).
  • Meta-analyses aggregating many weak, questionnaire-based studies are seen as especially unreliable, generating flip‑flopping claims (coffee, wine, meat, sweeteners, etc.).

Self‑Reporting Inaccuracy

  • Consensus that people misreport food, alcohol, smoking, exercise, and sex, often systematically:
    • Underreport foods seen as “bad”; overreport “good” foods.
    • Different groups misreport in different directions (e.g., “frat vs. Mormon” example).
  • Even trained professionals are said to mis-estimate portion sizes badly; visual estimates off by ~40–50% in one cited CVPR paper.
  • Time-scale issue: short food logs vs. long-term outcomes (decades) further weakens causal inference.

Calorie Tracking & Personal Practice

  • Many describe weighing ingredients and using apps (MyFitnessPal, Cronometer, Carb Manager, etc.), often only for weeks or months to “calibrate” portion intuition.
  • Common strategy: precisely track calorie‑dense items (oil, cheese, nuts, meats, sauces) and ignore low-calorie vegetables/spices.
  • Eating out is repeatedly called the biggest source of uncertainty; users resort to aggressive overestimation or avoiding restaurant food when cutting.
  • Several note you don’t need precision; consistency plus feedback via body weight lets you adjust.

Tech & Automation Ideas

  • Proposed solutions: AI + cameras, LiDAR portion estimation, barcodes, connected kitchen scales, continuous glucose monitors, wearable chewing detectors.
  • Current food‑photo apps are viewed as better than recall surveys but still quite inaccurate, especially on portion size and mixed dishes.

Controlled Feeding & Ethics

  • Some argue only tightly controlled feeding trials (hospital, prison, remote “boot camp” settings) yield rigorous data, but these are expensive, invasive, and may not generalize to normal life.
  • Using prisoners is raised and criticized on ethical and ecological‑validity grounds.

Broader Debates

  • Calories‑in/calories‑out (CICO) is defended as physically true but admitted to be hard to measure and implement; others say it’s descriptively true but not a useful planning tool.
  • Strong emphasis on satiety, ultra‑palatable foods, and psychology: tracking works partly by forcing mindfulness, not mathematical accuracy.
  • Some commenters see nutrition science as “deeply unserious” given reliance on self-report; others argue imperfect methods are still better than abandoning the field.